Captcha-test is a project mainly written in ERLANG and SHELL, it's free.
test mochi/captcha/mysql
Captcha mochiweb application, running at http://thijsdezoete.nl:8080/ Tutorial @ http://beebole.com/en/blog/erlang/how-to-implement-captcha-in-erlang-web-application/
Added mysql in the mycaptcha.erl file to store all captcha's codes and hashes
Enjoy!